Heating system



April 1943- D. GREGG 2,316,417

- HEATING SYSTEM Filed Dec. 6, 1941 s Sheets-Sheet 1 all David Gre g] April 13, 1943. o. GREGG 2,316,417

HEATING SYSTEM Filed Dec. 6, 1941 3 Sheets-Sheet 2 April 13, 1943. D. GREGG HEATING SYSTEM Filed Dec. 6, 1941 5 Sheets-Sheet s Patented Apr. 13,1943 2,316,417

HEATING SYSTEM David Gregg, Caldwell, N. J., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application December 6, 1941, Serial No. 421,979

'3 Claims. -(Cl. 237-9) This invention relates to heating systems, and more particularly to a steam heating system for aircraft cabins.

Aircraft cabin heating systems in use today are usually of the steam type, wherein a flash boiler situated in the engine exhaust stack is employed as the steam generating unit for a system including a steam radiator disposed in the air intake conduit of the craft. One of the serious problems encountered in heating cabins is that of obtaining even and uniform heat control throughout the cabin under a wide range of external air temperatures, and the conventional systems have failed to effect suitable heat control required for modern transports.

It is an object of the present invention to provide a steam heating system wherein thermostatic control elements are positioned at a plurality of different points in the air induction system.

It is a further object of the invention to provide a thermostatic control of air in plural stages to minimize the temperature change through which the air need be raised upon a demand for heat.

, Other objects include the provision of a novel thermostatic control device for regulating the amount of water to be fed to a steam boiler, and also the provision of a steam system for heating entering air wherein thermostatic control is provided for air at different points in the heating system.

Other objects will appear from a study of the following specification when made in conjunction with the attached drawings, throughout which like numerals designate like parts.

Fig. 1 is a schematicdiagram of one embodiment of the heating system of the present invention.

Fig. 2 is a longitudinal sectional view of a thermostatic flow control unit embodied in the heating system of the present invention.

Fig. 3 is a cross-sectional view of the unit shown in Fig. 2, taken along the line 3--3 of Fig. 2.

'tion l5, which in turn is connected directly to the airduct l2 within cabin l0.

The steam heating system of the present invention includes a water supply tank It, which-is connected by a water pipe l1 to a boiler feed pump l8 of conventional design, the output of which is connected through another water pipe i 9 to two parallelbranches. including first, a water conduit 20, a thermostatic flow control element 2| having a thermal transfer head 22 pro jecting into cabin l0, and a water delivery pipe 23, which is connected to the input of the flash Fig. 4 is a side elevation of the unit shown in Fig. 2; and

Fi 5 is a front or end elevational view of the same unit.

Having reference to Fig. 1, there is shown an aircraft cabin Ill, into which open a plurality of vents I of an airduct I 2, having branch members I3. Air from the atmosphere is received through a. duct I4 containing an enlarged porboiler 24 by means of a conduit 25. The second branch includes a water supply pipe 26 connected to another thermostatic flow control device 21 having a thermal transfer head 28, the output of which is connected, by means of a water delivery pipe 29, to conduit 25 and boiler 24. Boiler 24 is contained in the exhaust stack 30 of an aircraft engine (not shown), and the output of flash boiler 24 communicates with a steam radiator 3| through a steam pipe 32.

- The thermostats or thermostatic ilow control devices, 2| and 21, will be explained in detail below, but primarily, their function is to permit water to flow through their respective branches into the boiler 24 until a particular temperature for the surrounding air has been attained, upon which water flow through one or both of the branches may be stopped.

Water tank I 6 may be provided with a pressure relief valve 33 of any conventional design in order to prevent the possibility of destruction of the tank by high steam pressure, and with a vacuum valve 34, of any conventioned design, which serves to prevent the formation of low pressures within tank I6 upon condensation of steam therein.

. Water from tank I6 is pumped through the densed steam returns to water supply tank N by way of a return conduit 35.-

Under certain conditions of operation, both flow control elements 2| and 21 will cut oil flow to boiler 25, and since boiler feed pump is intended to operate continuously, a by-pass conduit 36 is provided 'to prevent excessive pressures from building up when flow through control elements 2| and 21 is stopped. A relief valve 3'1 is connected to the by-pass conduit 86 to permit return of water automatically from water'pipe l9 back to the input of pump [8 when the pressure means of the present invention that water shall be fed to the boiler 24 through the thermostatic control device 21 independently of water flowing through the thermostatic control device 2|, until the temperature of the air passing by the thermal transfer head 28 shall be equal to the temperature desired within cabin III. In this case, we will assume that control device 2'! acts to stop flow of water thereth rough when the air passing through conduit I2 adjacent the head 28 is 70 degrees.

Air entering the cabin at 70 degrees will be too cool to maintain the cabin temperature at '70 degrees under normal conditions, and therefore. the thermostatic control device 2| will permit water to be delivered therethrough to boiler 24 until the air adjacent the thermostatic head 28 shall attain the temperature of '10 degrees. Prior to the cut-oil. of water flow through thermostatic control device 2'|that is, prior to the at-.

and once it has been warmed to '70 degrees, the

volume of steam necessary to increase the temperature of the air flowing into cabin l through vents II, in order to maintain '70 degrees in cabin I, need be only that amount supplied through the thermostatic flow control element 2|.

A knob 39 projects from the casing of themestat 2|, and, as will be described below, the cabin temperature at which water is to be cut oil through thermostat 2|, may be selected through a suitable setting of the knob. A similar knob 40 is carried. on a shaft 4| projecting through the casing of thermostat 21 and also to. a point outside the air duct l4.

The thermostatic control devices 2| and 21 may incorporate identical thermo-sensitive and regulating valve structure, and therefore, in Figs. 2 to 6, the description'of these parts of the thermostatic control device 2l is applicable to device 21.

Housing 88 has an open end fltted with a closure plate 42, which is held in gas-tight engagement with housing 8| by means of a plurality of screw-studs 48. This housing also has a screw-threaded aperture 44, which carries a gland nut 48, having an integral extension forming the thermo-transfer head 22. This head carries a series-oi! heat radiating flns 48 exterlorly of a' cylindrical chamber 41. A flexible metallic bellows or :Sylphon 48 has one end welded or brazed to a metallic collar 49 fitted tightly within gland nut 48, which has one end welded to gland nut 48 at point 50. The other end of flexible bellows 48 has a gas-tight connection with the flat end face II of a plunger 82. The outer-- most end of chamber 41 is formed into a screwthreaded cap 84, which flts upon boss 88 with a gas-tight connection. It will thus be seen that chamber 41 is a gas-tight chamber or variable volume by virtue of the flexible bellows 48. A quantity of air or any other gas, or a liquid such as alcohol, carbon tetrachloride, or the like, is al-' lowed to flow through screw-threaded boss 82 prior to the application of cap 84, and thus, the fluid within chamber 41 may be at any desired pressure.

Plunger 52 extends within housing 88 and carries at its end a knife edged bearing point 85,

which rests against one end 56 of a loose link 81, contacting, at its other end 58, with a valve 'rod 88. Valve rod 58 extends within a valve chamber 60, which has transverse openings 8| ,and 82 opening thereinto and aligned with each other. A piston valve 88 is-carried on valve rod 88, and in the position shown inFig. 2, it closes ofl communication between transverse openings 8| and 82. Valve 68 also carries a pin 84 pro- Jecting in a direction opposite to valve rod 88, and this pin is of such length that when valve 82 is moved to the left, as will be described later, it clears openings 8| and 82 so as to permit communication'between these openings. A helical spring 88 bears against the left-hand face of valve 88 and acts to return valve 88 to the closed position shown under conditions to be later described.

Link 81 is pivoted, by means of a pin member 88, to the parallel arms 61 of a bracket member 88. The horizontally disposed portion of bracket 88, as viewed in Fig. 2, is a hollow cylindrical member 88 confined within a cylindrical casing 10,- having an inwardly extending flange Ii atits right end, and enlarged boss portion 88 at its left end, forming an integral end wall of housing 88. A piston 12 is confined within cylindrical casing 10 and is slidable therein, and is retained on cylindrical portion 89 of bracket 88 by means of a conventional retaining ring 18. A helical spring 14 has one end bearing against inwardly directed flange II, and its other end bearing against the inner face of piston 12. Action of spring 14 is such that the end face I! of bracket 68 is urged to the left against the cam face 18 of a cylindrical cam member 11. Cam member l1 carries a stub shaft 18, which is home within an aperture 18 formed in the end wall of casing 88, and terminates in the knob 88.

Housing 88 has a peripherally extending attaching flange 8| for attachment, by any conventional means, to the wall of cabin i0. Cylindrical casing I8 has a series of apertures 82 toward the left end thereof, which open into valve chamber Bil, which also has an opening 88 formed below valve chamber 88, and into which is fitted a screw-threaded pipe connecting member 84 carrying a drain pipe 8!.

The front or manual control end of flow control element 2| is shown in Fi 5. An ,arcuate scale member 86 is shown disposed above the threaded boss 88, upon which is carried a screwindex end of knob 48, and this scale bears indicia of a temperature range through which the thermostat is designed to exert control. It will be understood that the knob 88 is readily accessible to the steward or any personin the cabin |8 who desires to set the thermostat for a particular cabin temperature. The knob 48 of thermostat II, which performs the same function as does knob 88, will ordinarily be accessible for periodic adjustment by a crew member, so that the temperature of entering air may be regulated by a flight or maintenance crew member, although it is intended that thermostat 21 be set before a particular flight to a flxed cut-off.

temperature, and not be adjusted during flight.

It is believed that the operation of the system of Fig. 1 will be clear from the above description, and the operation of thermostats 2| and 21 to control the flowof water to boiler 24 will'be fully understood from the above, description, taken with the following explanation, particular referincreased pre'ssureof the fluid contained therein,

and plunger 52 will be moved to the right. Upon a lowering of the temperature about head 22, the-fluid within chamber 41 will become cool, the volume of chamber 41 will therefore become less,

.and plunger 52 will move to the left. 'I'heilns 48 aid in the rapid transfer 01' heat to chamber 41 from the surrounding air or from chamber 41 to the surrounding air, depending upon the direction of temperature change.

Assuming that knob 39 has been set for a cutofl! temperature of '70 degrees F,, and that the air surrounding head 22 is at less than this temperature, then plunger 52 is retracted somewhat into chamber 41, and the thermostatic control device is so designed that in this retracted position of plunger 52, spring member 85 forces valve 83 to the right of the position shown, and thus, through the movement of valve rod 59 to the right, the upper end 56 of link 51 will move counterclockwise about the pivot pin 66. Flow of water into valve chamber 60 through opening 6|, and from chamber 60 and opening 82 through delivery pipe 23 will be established. Of course, as the water thus flows through thermostat 2| it is delivered to create steam in. the boiler 24, and thus, the temperature of air adjacent the heat transfer head 22 increases. As the gas pressure in chamber 41 increases with temperature, the plunger 82 is moved progressively to the right, and when the selected cabin temperature has been attained, valve 63 will have been forced by the right-hand movement of plunger 62, as transmitted through link 51 and valve rod 59, to close transverse openings 6| and 62, and thus, stop i'low of water through thermostat 2|.

With cabin temperature at 70 degrees, and thermostat 2| in its cut-oil condition, as shown in Fig. 2, if the control knob 38 is movedto maintain a lower cabin temperature, for example 65 degrees, then cam face 16 presents a contact point of less axial projection to end face 'il, and-spring i4 forces piston i2 and bracket 68 to the left. Since the position of plunger 62, and therefore, bearing point 65, is fixed by the temperature within chamber 41, translation of bracket ll to the left will cause the end 58 of link 5710 i'orce valve rod 8! iurther'to the left, and of course, this movement merely continues to keep openings 6i and 62 out oi communication, so that water flow is prohibited. The temperature about head 22 will continue to decrease, and the ga in chamber 41 will gradually cool, allowing plunger 62 to be retracted into chamber 41. This retraction moves bearing point 66 to the left, and spring 66 acts to rotate link 51 counter-clock wise about pin 66 until the air about head 22 falls to 65 degrees temperature, at which point pipe 85.

desired level.

valve 63 has moved to the right suiiiciently to establish water flow through openings GI and 62, and water is then fed to boiler 24. The resultant steam raises the temperature about head 22, and at 65 degrees, plunger 52 has traveled to the right sufficiently to again move valve 63 to cut-oil position, thus stopping the formation of steam and the further rise of temperature in cabin It.

It will be seen that thermostatic control device 2| thus acts to maintaina predetermined temperature in cabin I 0, and that the flow of water to boiler 24 is permitted only when heatis demanded to raise the cabin temperature to its Small amounts of water that may settle in the chamber 60 are carried back to tank 1 6, or are otherwise disposed of through the drain result it only a single thermostatic flow control device within the cabin were employed,

In the conventional cabin control system utilizing a single thermostatic control or a single stage oi thermostatic control, air in the neighborhood of zero degrees F. is warmed to some temperature in excess of cabin temperature in order that the cabin temperature may be maintained at a desired level. When the desired cabin temperature is attained, the temperature of the entering air begins to fall, and soon. cold air at exterior atmospheric temperature is entering the ventilating ducts. 1

By means of the two-stage system of the present invention, the cabin is virtually flying in an atmosphere at 70 degrees or at any other. de-

. sired temperature, since all the entering air, re-

gardless of the heat demand in the cabin, is maintained at a desired (preferably, cabin) tern.- perature. Any demand for cabin heat is readily met, since the temperature change ofair to be eifected is much less than that to be eilected in the conventional system. Since the temperature change required in the present system is less and is subject to direct control, it is apparent that excessive hot spots in the openings of the ventilating ducts into the cabin will be avoided. and in fact, the temperature gradient between the thermostat in the cabin and any part in the cabin is kept to a minimum.

While only one embodiment of the present invention has been shown in the drawings, it is to be understood that various changes may be made without departing from the scope of the present invention. For'this reason, it is intended not to limit the invention by the description herein given as an example, but solely by the scone oi the appended claims.

What is claimed is:

l. A cabin heating system comprising a flash boiler, a steam'radiator, an air duct disposed about said radiator and having ventilating openings to the cabin, a water reservoir, a feed water pump connected to receive water from said reservoir, said flash boiler, said radiator and said feed water pump being in a closed series circuit, a first thermostat located in said duct, a second thermostat located in the cabin, a water connection through said first thermostat and extending between said feed water pump and said flash ply tank, a water connection between said radia-' tor and said tank, a boiler feed pump, a water connection between said water tank and said pump, two parallel water pipes connected between said pump and said boiler, a thermostat connected in each of said parallel pipes between said pump and said boiler, one of said thermostats being located in said conduit, the other being located in said cabin, and thermostatically actuated control means associated with each of said thermostats for controlling the flow of water from said pump to said boiler in accordance with the temperature or air within said conduit and within said cabin.

3. A heating system comprising a cabin having ventilating ducts, an air input conduit connected thereto, a steam radiator in said conduit, a boiler connected to said radiator, water teed supply means connected to said boiler, a water return conduit connected between said radiator and said water feed supply means, parallel flow branches between said feed water supply means and said boiler, a first thermostat located in said conduit adjacent said radiator, a second thermostat located in said cabin, flow control means in one of said branches actuated by said first thermostat to stop flow of water therethrough when the temperature of air in said conduit attains a definite temperatureand additional flow control means in the other or said branches actuated by said second thermostat to stop the flow of water therethrough when the air in said cabin reaches a desired temperature.

' DAVID GREGG. 

